Electronics and programming interspersed at various levels of difficulty. Sorry about some of the images not loading, it's a problem with blogger/blogspot.

Saturday, January 10, 2015

Ghetto remote Wii sensor bar

We had some guests coming over and thought of setting up the Wii to work with a cheap beamer. Oh, and only had a few hours to do that.

However, the cable for the Wii sensor bar is only around 3m and it was required to go about 6m. I can either cut it away, add some wire and be done or try to make it work from a distance.

Here's how to make your own remote bar with no damage to the original, in just a few minutes.

You need a glue gun, some resistors (2x100 ohms + 20 ohms or 120 ohms + 100 ohms) some wire and some pins. You also need a 12V supply to power everything up, I had a motorcycle battery in for the winter.

As it turns out, the sensor bar is just an array of IR LEDs. I've measured the output of the Wii and is around 7.5V. The sensor bar takes around 68mA.

The quickest way to do this was to 'design' a resistive divider:

Instead of the 120 ohm resistor I used 100 + 20 ohm resistors, in series.
How I determined those values was mostly a guess process: I used my adjustable power supply and increased the voltage until the bar was the same brightness as what the Wii was providing, while looking through the mobile phone camera.
You can use 100 ohms for both resistors and come up with a valid circuit as well, just a bit brighter.

To make a non-destructive modification I've molded everything around the original connector.
If you look inside the translucent connector below you will see two pins from a typical breadboard header. In a pinch, you can also use needles or pins.
They have to go inside the sensor bar connector and touch the walls.

The ground/minus side on the original connector is the slanted one (right-side in the picture above).
After the pins were set up to touch reliably on the contacts inside the connector, I sprayed the original connector with WD40 for better release, then I started putting layers of hot glue. I stopped from time to time to check that the connection is still ok.

Actually it took me longer to write this and to take pictures than the actual process, which was around 3 minutes for the hot-glue part and 5 minutes for everything else.
The resistors were packed in red electrical tape, that's the bulge you see in the 1st and 3rd pictures.

Battery life:

Power consumption: 12V / 220 ohms = 0.054A. With a (motorcycle) battery rated at 10Ah I would get 10/0.054=185h which means 7.7 days. I haven't measured the actual current used but it should be a bit lower -> more battery life.
With 100 & 100 ohms resistors you would get 60mA consumption and 166h usage which means 7 days, but increased remote sensitivity.
If you choose your own values you should probably not exceed 100mA.
The resistor divider gets a bit warm if left for an entire day but as long as it's not hot to touch it should be ok.

Bonus

Makeshift beamer stand out of a tripod:

Bonus 2

Makeshift beamer screen from a greenscreen stand and some white cloth.

You can also barely make out the sensor bar (black thing) stuck with tape on top of the screen. Afterwards, I've added some small neodymium magnets to the bottom of the sensor bar, since the tape eventually peels off from the screen.

Hi, thank you for the information unfortunately I have wallpaper on the ceiling as well. It will either get smoked or even catch fire. If the wallpaper does not, then probably the sheet cloth will.If missing the bar completely, one can steer the wiimote with a lighter kept at arms-length.